Abstract
A deficient mismatch repair system (dMMR) is present in 10-20% of patients with sporadic colorectal cancer (CRC) and is associated with a favourable prognosis in early stage disease. Data on patients with advanced disease are scarce. Our aim was to investigate the incidence and outcome of sporadic dMMR in advanced CRC. Data were collected from a phase III study in 820 advanced CRC patients. Expression of mismatch repair proteins was examined by immunohistochemistry. In addition microsatellite instability analysis was performed and the methylation status of the MLH1 promoter was assessed. We then correlated MMR status to clinical outcome. Deficient mismatch repair was found in only 18 (3.5%) out of 515 evaluable patients, of which 13 were caused by hypermethylation of the MLH1 promoter. The median overall survival in proficient MMR (pMMR), dMMR caused by hypermethylation of the MLH1 promoter and total dMMR was 17.9 months (95% confidence interval 16.2-18.8), 7.4 months (95% CI 3.7-16.9) and 10.2 months (95% CI 5.9-19.8), respectively. The disease control rate in pMMR and dMMR patients was 83% (95% CI 79-86%) and 56% (30-80%), respectively. We conclude that dMMR is rare in patients with sporadic advanced CRC. This supports the hypothesis that dMMR tumours have a reduced metastatic potential, as is observed in dMMR patients with early stage disease. The low incidence of dMMR does not allow drawing meaningful conclusions about the outcome of treatment in these patients.
Publication types
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Randomized Controlled Trial
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing
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Adenocarcinoma / drug therapy
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Adenocarcinoma / genetics*
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Adenocarcinoma / secondary
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Adenocarcinoma, Mucinous / drug therapy
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Adenocarcinoma, Mucinous / genetics*
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Adenocarcinoma, Mucinous / secondary
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Adult
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Aged
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Aged, 80 and over
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Antineoplastic Combined Chemotherapy Protocols / therapeutic use
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Camptothecin / administration & dosage
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Camptothecin / analogs & derivatives
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Capecitabine
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Carcinoma, Adenosquamous / drug therapy
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Carcinoma, Adenosquamous / genetics*
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Carcinoma, Adenosquamous / secondary
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Clinical Trials, Phase III as Topic
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Colorectal Neoplasms / drug therapy
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Colorectal Neoplasms / genetics*
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Colorectal Neoplasms / pathology
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DNA Methylation
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DNA Mismatch Repair / genetics*
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Deoxycytidine / administration & dosage
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Deoxycytidine / analogs & derivatives
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Female
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Fluorouracil / administration & dosage
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Fluorouracil / analogs & derivatives
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Humans
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Immunoenzyme Techniques
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Incidence
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Irinotecan
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Male
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Microsatellite Instability
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Middle Aged
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MutL Protein Homolog 1
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Nuclear Proteins
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Organoplatinum Compounds / administration & dosage
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Oxaliplatin
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Prognosis
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Promoter Regions, Genetic / genetics
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Randomized Controlled Trials as Topic
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Survival Rate
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Treatment Outcome
Substances
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Adaptor Proteins, Signal Transducing
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MLH1 protein, human
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Nuclear Proteins
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Organoplatinum Compounds
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Oxaliplatin
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Deoxycytidine
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Capecitabine
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Irinotecan
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MutL Protein Homolog 1
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Fluorouracil
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Camptothecin